Sorry if this is long winded. So I went to the track tonight to see what the new setup has. After my clutch exploded last year and took out my stock block, I built a stock bore brand new block LS2 with forged Wiseco -3.2 cc forged pistons, scat H beam rods with a stock crank. I installed .033 cometics to keep the compression up (61cc heads) and stuck my old heads and cam in it. It hasn't run what it did (best trap tonight was 113.75 compared to 116 on the previous setup in worse weather on a stock slipping clutch that had shorties and a FAST90. So after a couple of runs against the same 5.0 mustang I noticed smoke from my car in his headlights and decided to look around and see what I could find anything. I found quite a bit of oil around the vacuum line from the valve cover to the intake (vararam setup). I decided to temporarily plug them both and see if it stopped. This was a big mistake though because the very next run it blew the dipstick out and sprayed oil all over the passenger side. I called it a night and topped off the oil Once home I realize that the crank case pressure was high enough to blow out the rear main seal as well. The new engine has under 2000 miles on it, so the first thing I blamed was the rings. I have felt like its been down on power since the rebuild just by judging off of how it ran against friends cars. The low traps confirmed it. I then did a compression check and I was expecting the worst. I came away with 180+- across the board. I don't have access to a leak down right now either. What else can cause this crank case pressure? The coolant is still clean and at the top of the radiator so headgaskets seem good. Im still leaning towards rings but I wanted to see what you guys thought.

 

You can put a breather on the oil filler with a check valve to relieve the pressure from the blow by. Without a check valve it'll skew fueling under vacuum. If the blow by is getting worse, run a leakdown test, you may have ring/ringland issues.

There was a GM bulletin on stock LS2's to replace the filler cap with a vented one. They had PCV issues from the get go. I had one on my LS3 for a while until I got a better looking one.

 

Thanks, it's not a boosted motor, just a simple heads can ls2 that happens to be forged. A leak down test is next on the list though. I had not heard about the vented oil fill cap, I may look into that.

 

I looked at the one I bought, no GM P/N on it. My old '02 Monte Carlo 3.4 V-6 had a vented one though.

I have a modified Metco breather from JRE with a check valve in it. He has it with adapters for the stock twistlock and in my case the Holley threaded covers.

 

My old 402 LS2 was blowing my dipstick out,It ended up being my rings,Also when you assembled the engine withe the .033 head gaskets did you mock it up first and check your clearance between the cylinder head and the piston?,Thats going to be a pretty tight clearance i had .040 gaskets and it was damn near touching the head.,i get all motors are different just trying to help.

 

Thanks, I am leaning towards rings. I re did a few of the cylinders yesterday and then put a bit of oil in the cylinder and re ran the test, most picked up to 220 over the dry test of 180ish. I don't know what is a normal jump in pressure after using the oil though. I did check P/v clearance and had plenty. The factory pistons sit above the block deck while the wiscoes are 0 decked and have valve reliefs, so the headgaskets needed to be quite a bit thinner to come close to 11:4.1 that I was running with the stock block setup.

 

Well zero deck still sit a little above or below the block, what did ur quench end up at?

 

Just depends on the volume of oil you added, it doesn't compress so it raises the compression ratio by taking up space.

I'd do a leakdown test and go from there.

 

That TSB only applies for vehicles when the PCV freezes up in -30*F temps. I have a stock PCV system & a catch can on my 418 LS3 stroker without blow by issues. I'm concerned about the OP using a .033 head gasket. The piston may of hit the head & pinched the top ring lands.

Russ Kemp

 

Correct !!! .033" is awefully tight. I recently pulled apart a 7000rpm street stock 350 that the KB hypers were out of the hole .018" with .051" headgaskets and clearly the pistons were touching the chambers. Now the piston to wall clearance on hypereutectic (like stock LS) is .001"-.0015" whereas the forged stuff is usually .004"-.0055". That piston by design will rock more in the bore at TDC(directional change). It may not have broken off the ring land chunk yet but perhaps has pinched itself.

 

I have .04 gaskets and pistons .008 out of the hole... so thats .032 on a 7500rpm 4.125 stroke 430

Of course, I also run a vacuum pump to control pressure and my dome pistons have a very... interesting shape. Some combos are worse then others, but you just need better venting. Vent the valley, and vent each valve cover. If the stock vents arent enough, make bigger ones. It's so god damned simple, and it seems to blow so many people's minds. You could put 20 breathers on a valve cover to the atmosphere and the engine will run fine, i promise.

 

Well I'll be working on the venting soon. I did the leak down today and all cylinders were 9-10% which isn't incredible but within spec and very consistant. I probably put too much oil when I did the wet compression test, which skewed that number a bit. I'll be replacing the rear main seal, although it seems to have stopped and then installing a catch can and better vent setup. The fresh air line from the throttlebody to intake was kinked pretty bad as well. Thanks for the advice. Btw there is plenty of p/v clearance, the pistons have valve reliefs.

 

look at http://mightym0use.wix.com/mm-solutions hes a member on here also. I just bought a can from him. He is very knowledgeable

 

Mightymouse makes quality stuff, JD. I have the RevExtreme can on my car. Based on their lack of communication and the time it took to receive it in the mail, I would encourage you not to get the one I have.

 

from the time i emailed mightymouse to the time i got my can was less than a week btw. great service

 

I would not use a "breather filter" on any part of the engine save for the air intake itself.

We sure do have the Rev catch cans avail and are top quality pieces.

A properly operating PVC system is more what you need to look at. If we can help you further please let us know. Otherwise, it may be a possible ring issue, which sadly can be common on quite a few stock engines and yes even fairly fresh builds from the machine shops.

 

Why not? Every real catch can is going to have one sitting on top, you cant recirculate two -10 lines. Well, I guess you could, but why would you?

 

I am not sure why you would need 5/8 hose coming from the valve covers on a stockish engine. Everyone has their own ideas of how to set up the PCV system or do away with it. Alot of times it is a bandaid for an improperly machined short block.

 

It's not stockish, look at his parts list and pretend you know a thing or two about how compression works with a regular ringpack. All that pressure is going to the bottom end of the motor once it goes past the rings. It's not rocket science to figure out... no tight clearance hyper pistons here...

 

As a vendor, I am not going to get into a pissing match over who knows more about what. Nor will I put your down for having a contradictory opinion.

He is using a stock LS2 bore size and stroke. The only thing not stock are the pistons and rods, but still that is no reason to be recommending a 5/8" hose like you just alluded to.

I would look at a proper PCV system first before delving into any more complicated matters.
It really sounds like improperly setup rings or PTB/machine work to me.